1. Field of the Invention
This invention relates to an improved connector and a contact set assembly employing the improved connector for use in a test site and, more particularly, to an improved contact set assembly for an IC handler, employing a controlled impedance transmission line connector affording improved mechanical and electrical "device-to-test head" contact. The IC (integrated circuit) devices to which the invention relates, but is not limited, include both conventional IC packages such as DIP's (dual-in-line packages) and also higher density packages used in LSI and VLSI technologies and having high pin counts, such as leadless and/or leaded chip carriers (LCC) and small-outline (SO) packages.
2. Description of the Prior Art
IC handlers vary in their construction and design, from manual and/or semi-automatic handlers which provide basic input- and-output movement of devices across a tester head, to sophisticated, essentially fully automated systems which are capable of communicating with a host computer. Sophisticated handlers are capable of handling in excess of 10,000 to 12,000 or more devices per hour with controlled environmental conditions. Handlers may be dedicated to testing of devices of a single predetermined configuration, or adjustable, to accommodate devices of different sizes and configurations.
As has been recognized in the prior art, handlers present a difficult design problem, since they must be easy to operate and of sufficient speed to be economical in a production operation, while solving numerous electrical, thermal, environmental, and mechanical problems necessary to the handling function to enable accurate testing operations. Device-to-test head contact is a major electrical problem. Thermal problems result from the need to cool and heat devices before testing, both rapidly and accurately, to simulate actual operating conditions of the devices (e.g., environmental temperatures from -60.degree. C. to +160.degree. C.). The handler also must withstand other environmental conditions, such as static voltages, humid locations and frost build-up during cold-environment testing operations.
Mechanical problems include the need to achieve high speed operation for any of a variety of package sizes, yet with minimization of wear to the handler parts, and particularly to the probes which make contact to the pins or contact areas of the IC devices.
An example of the general handler function in transporting devices to a test site is illustrated in FIG. 1; the schematically illustrated flow of devices corresponds to that performed in high speed IC handlers manufactured by Micro Component Technology Inc., assignee herein. As schematically shown in FIG. 1, the handler 10 includes a supply trough 12 which supports a plurality of DIP's 13, 14, 15 . . . in a gravity feed position. For this purpose, the feed trough 12 of a commercially available MCT system is at an angle of approximately 35 degrees from the horizontal. A solenoid actuated stop 16 retains the DIP's 13, 14, 15 . . . in the feed position.
A shuttle mechanism 18 is maintained in a normal receiving position, shown in solid lines, for receiving a single DIP from the trough 12 when the solenoid stop 16 is retracted. The shuttle 18 then is rotated by actuator 19 to its dotted line, discharge position 18' in alignment with the output trough 20 to release the DIP carried thereby onto the output trough 20. The trough 20, due to its anglular position of about 35 degrees from the horizontal, effects gravity feed of the DIP down the trough 20 to a test station 22. A solenoid actuated stop 24 stops the DIP 23 when received at the test site 22. Although not shown in FIG. 1, a contact set assembly is mounted at the test site 22; it is actuated when a DIP is positioned at the test site 22 to make contact to the leads or contact pins of the DIP. After testing of the DIP, the solenoid actuated stop 24 is energized and retracted, thereby to release the DIP 23 to continue down the trough 20 to a receiving device, typically a sorter.
DIP's vary in size, typically from 300 to 600 mils in width, and have varying numbers of leads or pins, from as few as 6 pins (three pins on each of the two longer sides, such as on a 300 mil device) to 42 pins (21 pins on each of the two sides such as in a 600 mil device). Typically, the DIP contact pins are separated at 100 mil center line spacings.
The demand for high density packaging has resulted in higher pin count LSI and VLSI technology devices, known as lead-less or leaded chip carriers (LCC's). Such carriers come in a variety of package sizes and configurations with corresponding variations in the number of contacts thereon, such contacts typically being provided on all four sides of the generally rectangular package. Small outline (SO) packages as well present variations in package size and number of contacts.
These variations in sizes, configurations, and types of IC devices have presented substantial problems in the design of appropriate contact set assemblies for the test sites of handlers. Moreover, as the complexity of the IC package increases, along with the emergence of high performance testers for testing the ever more complex IC packages, the need for achieving electrical contact with minimal degradation of the test signals has increased. High performance testers today operate in the 50 to 100 MHz range, imposing stringent requirements on the handler function and particularly as to the device-to-test head contacts. In high speed testing of devices such as ECL (emitter-coupled logic) circuits, high speed TTL (transistor-transistor logic) and even some higher speed MOS (metal oxide semiconductor) circuits, the contacts, if not made properly, and/or if not made through sufficiently short electrical paths, can degrade the test signals to the point of defeating reliable testing of the devices.
A further significant problem is the need to electrically couple or decouple the IC close to the device itself, so as to eliminate both power supply noise and ground noise. Another significant problem is that of impedance matching from the tester to the pin of the integrated circuit. Mismatching causes reflections and ringing and degrades the testing waveform, especially in the case of dynamic parametric tests, severely impacting the capability of high speed testing, such as is required for ECL type signals. A further serious problem is that of cross-talk, and particularly as to noise coupling among the signal lines connecting the pins of the devices to a mother board or other connection associated with the testing equipment.
Prior art contact sets employed in handler test site assemblies fail to address these problems at all, or address them only inadequately. As those with skill in the art appreciate, the inadequate bypassing of prior art devices can cause significant variations in the voltage levels actually applied to the device under test, seriously affecting the capability of testing. Improper impedance matching can result in transients requiring delay intervals for stabilization before testing can be conducted, significantly reducing the through-put rate for testing of sucessive devices. The significance of the speed of testing can be appreciated with regard to testing of a 16K memory (having 16,384 bit memory devices). Transient characteristics created by improper impedance matching require a delay time interval to achieve stabilization prior to test; assuming accurate testing of each memory cell is to be achieved, the time required to conduct the test for a single such memory device thus is increased by a total of over 16,000 such individual delays. Thus, proper impedance matching is critical to achieving transient-free and thus high speed operation for the testing function.
Highly accurate testing also requires a contact set configuration which provides Kelvin contact. Frequently, prior art devices are incapable of affording Kelvin contact, particularly on LCC's.
These and other problems of the prior art test sites, and especially the contact set assemblies employed therein, are overcome by the contact set assembly of the present invention.